usleep(3) Library Functions Manual usleep(3)
NAME
usleep - suspend execution for microsecond intervals
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int usleep(useconds_t usec);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
usleep():
Since glibc 2.12:
(_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE
Before glibc 2.12:
_BSD_SOURCE || _XOPEN_SOURCE >= 500
DESCRIPTION
The usleep() function suspends execution of the calling thread for (at
least) usec microseconds. The sleep may be lengthened slightly by any
system activity or by the time spent processing the call or by the
granularity of system timers.
RETURN VALUE
The usleep() function returns 0 on success. On error, -1 is returned,
with errno set to indicate the error.
ERRORS
EINTR Interrupted by a signal; see signal(7).
EINVAL usec is greater than or equal to 1000000. (On systems where
that is considered an error.)
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│usleep() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
4.3BSD, POSIX.1-2001. POSIX.1-2001 declares this function obsolete;
use nanosleep(2) instead. POSIX.1-2008 removes the specification of
usleep().
On the original BSD implementation, and before glibc 2.2.2, the return
type of this function is void. The POSIX version returns int, and this
is also the prototype used since glibc 2.2.2.
Only the EINVAL error return is documented by SUSv2 and POSIX.1-2001.
NOTES
The interaction of this function with the SIGALRM signal, and with oth-
er timer functions such as alarm(2), sleep(3), nanosleep(2),
setitimer(2), timer_create(2), timer_delete(2), timer_getoverrun(2),
timer_gettime(2), timer_settime(2), ualarm(3) is unspecified.
SEE ALSO
alarm(2), getitimer(2), nanosleep(2), select(2), setitimer(2),
sleep(3), ualarm(3), useconds_t(3type), time(7)
Linux man-pages 6.03 2023-02-05 usleep(3)
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